This invention relates to sewing machines and more particularly to means for turning a workpiece in the sewing machine.
A sewing machine is disclosed in German Patent Specification No. 1,685,079. The torque in this German patent machine presses the edge of a workpiece in the area which is still to be sewn, against a guide edge responsive to an advance of the conveyor. In order to be able to produce seam profiles in corners, for example, at collar tips and the like, a turning device is mounted on the upper side of the workpiece to turn it by the necessary angle about the needle axis. Such a turning device is very complicated, because it requires a separate drive motor. The turning device is unsuitable for sewing curved seams, where direction changes occur between the individual stitches, because it is not possible to raise, re-apply and actuate within in each one stitching cycle in view of the sewing speeds that are used. There is also a considerable risk of deforming workpieces made from soft materials.
German Patent Specification No. 1,485,331 discloses a workpiece guidance device for sewing machines, in which the workpiece edges are folded over. At least one air set nozzle is provided to ensure that the workpiece always engages a guide edge in the folding device. The air jet presses the workpiece against the guide edge, at right angles to the sewing direction. It is also possible to provide air nozzles acting in the sewing direction, which compensate for the frictional forces occurring in the folding direction.
An object of the invention is to provide a sewing machine in which it is possible to sew workpieces in an edge-parallel manner. The workpieces are made from soft materials and may have curved or angular seam profiles which are followed by automatic guidance devices.